Interpretive Summary: Infections by the single-celled parasite, Toxoplasma gondii, are widely prevalent in humans and livestock. This parasite can cause devastating illness in congenitally infected children and abortion in livestock.
Scientists at the Beltsville Agricultural Research Center and a zoo in Kentucky report severe toxoplasmosis in ferrets and propose methods for its prevention. These results will be of interest to biologists, parasitologists, zoo veterinarians, and public health workers.

Technical Abstract:
An epizootic of toxoplasmosis occurred among 22 adult and 30 kit black-footed ferrets (Mustela nigripes) maintained under quarantine conditions at the Louisville Zoological Garden in June, 1992. Black-footed ferrets appear to be highly susceptible to acute and chronic toxoplasmosis. Clinical signs were observed in 19 adults and six kits and included anorexia, lethargy, corneal edema, and ataxia. Two adults and six kits died with acute disease. High antibody titers to Toxoplasma gondii were detected by latex agglutination and modified agglutination assay in 10 black-footed ferrets. One adult and six kits that died with acute clinical signs were necropsied and T. gondii-like organisms were found microscopically in multiple organs. Diagnosis of toxoplasmosis was confirmed by immunohistochemical staining with T. gondii for black-footed ferrets was not identified, frozen uncooked rabbit was the most likely source. Chronic toxoplasmosis resulted in the death of an additional 13 black-footed ferrets that were adults during the epizootic. Affected animals developed chronic progressive posterior weakness and posterior ataxia 0.5 to 5.75 yr after the epizootic began. Meningoencephalitis or meningoencephalomyelitis associated with chronic toxoplasmosis were identified at necropsy in all 13 ferrets. Precautions to prevent introduction of pathogens into the colony were insufficient to exclude T. gondii. Although toxoplasmosis may cause significant mortality in mustelids, the high mortality of black-footed ferrets in this epizootic was of concern due to their endangered status. This is the first detailed report of toxoplasmosis in black-footed ferrets.